Ultrastructural alterations of endothelium covering advanced atherosclerotic plaque in human carotid artery visualised by scanning electron microscope.

Human atherosclerotic plaque morphology at its various stages was extensively documented using light microscopy. However, much less is known of the ultrastructure of the human atherosclerotic plaque, in particular of ultrastructure of endothelial cells in atherosclerosis. Here, we analysed alterations of endothelial cells covering advanced atherosclerotic plaque in carotid artery using scanning electron microscope. Examination was performed on specimens from atherosclerotic lesions of the interior carotid artery, collected from 8 patients who had undergone endarterectomy. We found wide spectrum of pathological alterations of the luminal surface of atherosclerotic plaque. In dominant part of the vessel, endothelial layer was preserved but displayed pronounced irregularities in endothelial architecture including appearance of cuboidal cells. Some endothelial cells were covered by numerous microvilli and/or contained "craters" disrupting continuous surface of the endothelium. Platelets and leukocytes adhering to endothelium were frequently observed. There were also areas of the vessel lumen with endothelial denudation, in which the subendothelial surface containing fibrin proteins and collagen fibrils were visible. Interestingly, signs of proliferation of endothelial cells tending to cover the partially denuded vessel were observed. In summary, in scanning electron microscope, preserved endothelial cells of advanced atherosclerotic plaque displayed pronounced pathology; whether any of these changes represent the ultrastructural correlate of endothelial dysfunction remains to be established.